The present invention relates generally to hazardous material containment systems, and more particularly to an apparatus for containing a hazardous material as it is loaded into or unloaded from a bulk shipping container such as a tanker truck or a railroad tanker car.
The transportation and handling of hazardous materials, such as chlorine in its liquid or gaseous forms, presents many well known health and environmental dangers. Despite these dangers, many of the methods currently used to control such a leak are either prohibitively expensive, or ineffective in certain circumstances. As a result, the failures of systems associated with bulk shipping containers have produced many damaging hazardous material leaks.
One device currently used to control hazardous material leaks is an excess flow check valve. Such a valve stops material flow from a container when the flow rate is above a predetermined limit, known as the excess flow check valve set point. While excess flow check valves are effective in many circumstances, a large release can still occur if the flow rate of a leak is less than the excess flow check valve set point.
Another device used to control hazardous material leaks is a remotely mounted and activated shutoff valve. Such a valve may be used by itself, or in combination with one or more hazardous materials sensors. If a leak is detected, the sensors generate a signal causing the remote valve to close. A major drawback to this arrangement is that a leak may bypass a sensor location, and thus go undetected for some period of time. Also, there is no way to neutralize material released before the remote valve is closed.
Finally, the most effective of the prior techniques for controlling hazardous material leaks is the complete enclosure of a shipping container inside an environmentally sealed structure. Sensors and remote shutoff valves can be provided within the structure itself, allowing detection and complete containment of a hazardous material leak.
One of the drawbacks of such an arrangement is that in the event of a hazardous material release, the volume of air that must be controlled (absorbed or neutralized) is quite large. Therefore, neutralizing the leaked material requires a very large and expensive control system. Environmentally sealed structures are also quite expensive and immobile. Therefore, hazardous material users cannot always load or unload material into or from shipping containers in a safe manner.